Mr Trump’s 90-second statement on Saturday morning appeared to be his first full apology in a campaign laced with controversial remarks.

“I’ve said and done things I regret,” he said. “Anyone who knows me knows these words don’t reflect who I am. I said it, I was wrong, and I apologise.

“I’ve never said I’m a perfect person nor pretended to be someone I’m not. I pledge to be a better man tomorrow.”

However, he also tried to deflect the impact by attacking former President Bill Clinton.

Donald Trump has often found himself in hot water for public comments he’s made about women over the years. It turns out he’s said lewd and disparaging things in private as well. Go figure.

The videotape release comes at a most inopportune time for the Republican nominee, who was trying to use his running mate’s well-received debate performance on Tuesday to reboot his campaign after a week of distractions and controversy. On Wednesday he told a local news interviewer that his previous offensive comments about women – which have dogged his campaign since the first Republican primary debate last August – were made for the “purpose of entertainment”.

That explanation doesn’t fit with the boorish, newly married Trump shown on the video privately boasting about his efforts to seduce a married woman and have his way with whomever he pleases.

Now Mr Trump will enter Sunday’s debate with a new cloud hanging over his candidacy. It’s almost certain that one of the town hall participants will ask him about it. There may be no easy way to respond – but Mr Trump will have to find an acceptable answer. If he bungles it, nothing else he says during the 90-minute debate will matter.

“Bill Clinton has actually abused women, and Hillary has bullied, attacked and shamed his victims.

“We’ll discuss this in the coming days,” he said. “See you at the debate on Sunday.”

The second TV debate between Mr Trump and Mrs Clinton will take place on Sunday evening in St Louis.

Mr Trump recently said he would not bring up stories about Bill Clinton’s infidelities in the debate, after previously threatening to do so.

The latest opinion polls suggest Mrs Clinton is pulling ahead in key battleground states and Mr Trump will need a good performance at the debate to slow the trend.

‘I moved on her’

In the video, posted by the Washington Post, Mr Trump is heard bragging to TV host Billy Bush about trying to have sex with a married woman as well as kissing and groping others.

The clip was part of unaired footage of an Access Hollywood segment ahead of Mr Trump’s appearance on the soap opera Days of Our Lives.

“I moved on her and I failed. I’ll admit it,” Mr Trump is heard saying. “She was married. And I moved on her very heavily.

“I moved on her like a bitch, but I couldn’t get there. And she was married. Then all of a sudden I see her, she’s now got the big phony tits and everything. She’s totally changed her look.”

Later in the conversation, he told Mr Bush he was “automatically attracted to beautiful” women and often tried to kiss them.

“I just start kissing them,” he said. “I don’t even wait. And when you’re a star, they let you do it. You can do anything.”

Top Republicans have been incensed by the comments.

House Speaker Paul Ryan said he was “sickened by what I heard today” and rescinded his invitation to Mr Trump to attend the Republican Fall Fest in his home state of Wisconsin this weekend.

Senate majority leader Mitch McConnell said the comments were “repugnant,” adding that Mr Trump “needs to apologise directly to women and girls everywhere”.

Another senior Republican, John McCain, said there were “no excuses for Donald Trump’s offensive and demeaning comments”.